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New MRSA variant poses new concern for veterinarians, public health and medicine

Jun 06, 2011

By dvm360.com staff

DVM360 MAGAZINE

International Report -- A new study published in The Lancet Infectious Diseases reports that animals can act as a reservoir to a novel strain of methicillin-resistant Staphylococcus aureus.

In a scientific paper titled "Meticillin-resistant Staphylococcus aureus with a novel mecA homologue in human and bovine populations in the UK and Denmark: A Descriptive Study," Garcia-Alvarez et al say, "Here, we report the discovery of a strain of S aureus (LGA251) isolated from bulk milk that was phenotypically resistant to meticillin but tested negative for the mecA gene and a preliminary investigation of the extent to which such strains are present in bovine and human populations."

The study suggests that cattle can be a reservoir for human infection from tainted milk. Since pasteurization kills the MRSA variant, the risks to the food chain are small. However, there are associated risks for those who handle animals and byproducts, the study suggests.

Also, in this study the researchers discovered this new mecA gene that was not detected by confirmatory mecA tests (considered the gold standard for identifying MRSA).

According to the studies, "Although routine culture and antimicrobial susceptibility testing will identify S. aureus isolates with this novel mecA homologue as meticillin resistant, present confirmatory methods will not identify them as MRSA. New diagnostic guidelines for the detection of MRSA should consider the inclusion of tests for mecALGA251."